1. Field of the Invention
The present invention relates to a matrix liquid crystal display using an antiferroelectric liquid crystal to provide a matrix-driven display and to a method of driving such a display.
2. Description of Related Art
A known matrix liquid crystal display of this kind is described, for examples in OPTRONICS, No. 2, pp. 58-61 (1994). In this devices a de-select period in which pixels are deactivated, a select period in which only pixels necessary to display an image are activated, and a retention period in which the displayed state is maintained are successively repeated. Scanning electrodes on successive lines are driven such that the lines are sequentially scanned. In this way, a desired image is displayed.
In this driving method, if the contents of the display created by selected pixels are not completely erased during the de-select period, the image is not momentarily switched from a bright state to a dark state. Therefore, if a dark object moves on a bright background, the object is accompanied by a white tail. That is, the displayed image tails off.
In order to prevent this undesirable phenomenon, it is necessary to establish sufficiently long de-select periods. Furthermore, the response time between the instant when a positive or negative ferroelectric state providing a bright display is established and the instant when an antiferroelectric state providing a dark display is established varies with the operating temperature. In this case, the de-select period is increased as the temperature becomes lower. Accordingly, in order to prevent the displayed image from tailing off over a wide range of temperatures, it is necessary to establish the de-select period in such a way that the contents of the displayed image can be fully erased even at the lowest temperature.
However, if this scheme is adopted, the de-select period is too long at normal operating temperatures, and the retention period is too short. As a result, the brightness of the image in a dark state drops.